Synthetic textile treated with polyalkenoxy agents and corrosion inhibiting salts to prevent static electric charges



United States Patent 3,348,968 SYNTHETIC TEXTILE TREATED WITH POLYAL- KENOXY AGENTS AND CORROSION INHIBIT- ING SALTS TO PREVENT STATIC ELECTRIC CHARGES Duncan Robert Hulbert, Dennis Richard Sheard, and

Harold Frederick Brown, Harrogate, England, assignors to Imperial Chemical Industries Limited, London, England, a corporation of Great Britain No Drawing. Filed Feb. 20, 1964, Ser. No. 346,102 Claims priority, application Great Britain, Feb. 21, 1963, 7,069/63 1 Claim. (Cl. 117-138.8)

This invention relates to a process for treating textile materials such as fibres, yarns and fabrics particularly to reduce their tendency to acquire a charge of static electricity.

It is well known that textile materials, particularly those which are obtained from synthetic fibre-forming, hydrophobic polymers, have a marked tendency to acquire a charge of static electricity during processing such as carding, spinning or weaving, and in wear.

It has been previously suggested that such a tendency may be reduced by treating the textile materials with certain agents derived from the reaction products of agents containing one or more reactive hydrogen atoms, e.g. certain fatty acids, alcohols, phenols, amines, amides or mercaptans with varying amounts of an alkylene oxide, particularly ethylene oxide. Although such agents successfully reduce the tendency of the textile materials to acquire a charge of static electricity, they are not always effective under conditions of low relative humidity and, as we have surprisingly found at low temperatures, troublesome static charges may remain.

We have now found that these residual charges may be very markedly reduced by treating the textile materials with the agents mentioned above in combination with certain inorganic salts which are capable of ionising in aqueous solution. Many of such salts, however, suffer from the disadvantage that they cause corrosion of the metal surfaces of the machinery which is used in their application and during processing. We have further found that salts containing, as the anion, nitrite, carbonate, bicarbonate, tetraborate, ortho-phosphate, chromate, benZoate or silicate, when used in conjunction with condensates of alkylene oxide with fatty acids, alcohols, phenols, amines, amides or mercaptans, etc., at least two main beneficial effects are obtained. The corrosion of machinery used in textile processing is inhibited and the tendency of the treated textiles or textile materials to acquire a charge of static electricity even under adverse processing conditions is considerably reduced, other effects are improved behaviour during textile processing and in wear.

Thus, according to the present invention, we provide a process for treating textile materials such as filaments, fibres, yarns and fabrics substantially to obviate their tendency to acquire a charge of static electricity, comprising treating said textile material with a surface active polyalkenoxy agent in combination with a corrosion-inhibiting salt or salts so that rusting on a clean polished mild steel surface is prevented if said treated fibres, yarns and fabrics are brought into contact with said metal.

The polyalkenoxy agent is a surface active compound selected from one or more of the following ethylene and/or propylene oxide condensates which may contain either ethylene or propylene oxide units. The condensation products of ethylene oxide and/or the propylene oxide may be obtained by condensation with linear or branched chain saturated or unsaturated aliphatic, cycloaliphatic, aromatic or araliphatic, carboxy, amido, amino,

"ice

hydroxy or mercapto compounds. These condensation products may be further reacted with a linear or branched chain saturated or unsaturated aliphatic, cycle-aliphatic, aromatic, or araliphatic, carboxylic acid. The aliphatic, cycle-aliphatic, aromatic or araliphatic residue contains at least 8 carbon atoms and may contain further substituents such as hydroxyl, thiol, ether, thiolether and amino groups. The alkylene oxides which are preferably polyglycol condensates are capable of dissolving appreciable amounts of inorganic salts including our corrosion inhibiting salts, which is important in the absence of imbibed atmospheric moisture, i.e. when the materials are used under conditions of low relative humidity.

Non-aqueous solutions of the salts in polyglycol condensates show high bulk electrical conductivity properties, compared with polyalkenoxy condensates without the salts, so that they provide a conductive electric leakage path when present on hydrophobic synthetic fibres.

The presence of the dissolved salts in the polyglycol condensates increases the ability of the condensates to absorb moisture from the atmosphere.

The presence of imbibed atmospheric moisture further increases the solubility of the salts in the polyglycol condensate. In consequence there is a synergistic effect between inorganic salt and water when polyglycol condensates are present with the result that the polyglycol condensates then show antistatic activity at lower temperatures and relative humidities, than would be shown by the polyglycol condensates used without added salt.

It should be appreciated that although certain other inorganic salts may also improve antistatic properties, they would cause corrosion of textile machinery which is prevented when using our combination.

Such agents are usually made either by condensing a compound containing one or more reactive hydrogen atoms (e.g. an alcohol, phenol, carboxylic acid, amine, amide or mercaptan) with an alkylene oxide such as ethylene oxide, or by reacting such a compound with a polyglycol.

Examples of the polyalkenoxy agents thus described may be found in Surface Activity by Moilliet, Collie and Black pp. 466-490 (2nd edition) or in Polyethers Part 1. Polyalkylene Oxides and Other Polyethers, ed. by Gaylord, pp. 189-213 and 225-230.

The corrosion-inhibiting salt or salts have the general formulae (M +),,(X where the cation M+ is derived from a metallic element forming ionic salts, preferably an element in Group I-A of the Periodic Table of the elements, and in particular lithium, sodium or potassium, X- is a corrosion-inhibiting anion such as nitrite, carbonate, bicarbonate, tetraborate, ortho-phosphate, chromate, benzoate or silicate, and p and q are integers corresponding to the valencies of the cation and anion respectively. The anions referred to above are all effective in preventing visible rusting on a clean, polished mild steel surface.

Textiles and textile materials may be treated according to the process of the present invention by a variety of procedures. The alkylene oxide condensate and the corrosion-inhibiting inorganic salt or salts can be applied together from a solution or dispersion, or they can be applied from separate solutions or dispersions in separate stages.

In the case of a condensate of fatty acid with a low molecular proportion of ethylene oxide, it is preferable to apply the specified aqueous inorganic salt solution after the application of the ethylene oxide condensate, in a subsequent separate step.

In the manufacture of cold-drawable synthetic fibres when the filaments from which the fibres are made, are drawn at least twice their length, the ethylene oxide condensate is conveniently applied in a bath on a draw frame, before drawing the filaments at least twice their length,

Such solutions and dispersions may be applied to the textile by any known means. They may be padded on to the textile, applied from a rotating wheel dipping into them, or the textile may be impregnated with them by immersion, or they may be applied by jet or spray. Other agents which are used in textile processing may, if desired, be used in conjunction with the alkylene oxide condensate and the inorganic salt or salts.

In applying finishes according to the present invention to any textile materials amounts of from 0.05% to 0.30% on thetextile material of the alkylene oxide condensate and of 0.001% to 0.050% of inorganic salts are preferred.

The treatment may be carried out at normal or elevated temperatures and the treated textile material may be subsequently dried at any convenient temperature which has:

no harmful effect on the textile material.

The process of the present invention may be applied to any textile material containing at least a minor proportion of hydrophobic fibres, for example those made from polyethylene terephthalate, stereoregular polypropylene, a polyamide or polyacrylonitrile.

If the polyalkenoxy agent is sufficiently water-soluble it may be convenient to make up a concentrated stock solution or dispersion containing the polyalkenoxy agent together with the desired inorganic salt, and as much water as is required to bring the latter into solution. Such a stock solution may be further diluted with Water as required, and used during fibre manufacture, or for redressing purposes during, subsequent textile processing op-' Example 1 A non-ionic textile finish made by condensing lauric. acid with ethylene oxide in a molar ratio of about 1:9 (polyethylene glycol 400 monolaurate) was dissolved in water and deionized. It was applied to 75 denier (83.3 decitex) finish-free polyethylene terephthalate filament yarn by passing through the solution and then drying it. The strength of the solution was adjusted to give approximately 0.5% of the polyethylene glycol 400 monolaurate on the yarn. The eflectiveness of the finish as an antistatic agent was assessed by measuring the electrical resistance of 200 parallel lengths of yarn each 5 centimeters long at relative humidities of 20%, 65% and 75%, and at 21 C. Results are shown in line 1, Table 1, below. The lower the electrical resistance, the more effectively the finish diminishes the tendency to static charge formation, and vice-versa.

The experiment was repeated exactly as before except that this time potassium carbonate (anhydrous) was added to the polyethylene glycol 400 monolaurate solution to give approximately 0.014% anhydrous potassium carbonate on the yarn. Results are shown in line 2, Table 1, below, from which it is seen that incorporation of the potassium carbonate reduced the resistance of the yarn at each of the relative humidities by a considerable factor, i.e. the tendency of the yarn dressed with polyethylene glycol 400 monolaurate to static charge generation is considerably diminished by the addition of potassium carbonate. Even under the severe conditions, as regards static,

charge generation, of 20% R.H., addition of potassium carbonate renders the yarn less liable to static charge generation than yarn dressed with the nonionic finish alone at RH.

TABLE 1 Electrical Resistance/Ohms Agent 20% RH. 65% RH. RH.

1. Yarn dressed with polyethy- 7.1)(10 1.5)(10 5.0X10

lene glycol 400 monolaurate alone.

2. Yarn dressed with po1yethy 9.7X10 6.0)(10 2.7 X10 lene glycol 400 monolaurate and potassium carbonate.

0.2% dispersions of the following nonionic finishes were also made up:

A. Cetyl/oleyl alcohol condensed with ethylene oxide in the molar ratio 1:35.

B. Cetylamine condensed with ethylene oxide in the molar ratio 1:12.

C. Dodecyl mercaptan condensed with ethylene oxide in the molar ratio 1:6.

Portions of these dispersions were taken and various inorganic salts, as listed below, added to give solution concentrations of 0.002 equivalent per litre. These dispersions were applied to 50 denier (55.6 decitex) finish-free polyethylene terephthalate filament yarn by passing the yarn through and then drying it. The effectiveness of each formulation with respect to antistatic activity was assessed by measuring the electrical resistance of 200 parallel lengths of yarn each 5 centimetres long at a relative humidity of 65 From Table 2 below it can be seen that in each case addition of the inorganic salt results in a decreased electrical resistance as compared with nonionic finishes used alone, and hence the tendency of the yarn to static charge generation is reduced by the presence of the inorganic Example 2 Two samples of crimped polyethylene terephthalate staple fibre of mean denier 1.5 (1.67 decitex) and length 1.5 inches and dressed with an agent consisting of (A) 0.15% of a finish made by reacting 1 mole of stearic acid with approximately 9 moles of ethylene oxide, and (B) 0.15% of the same finish together with 0.004% of sodium nitrite were opened and made into laps and then processed on a carding machineThe latter was surrounded by a special chamber inside which the temperature and relative humidity could be varied independently. After opening and lap making the laps were conditioned in the card chamber prior to carding, and trials were performed on each lap under a variety of conditions of temperature and relative humidity. Any tendency towards troublesome electrostatic charge generation was detected by allowing the fibre to card, but instead of condensing the web into a sliver, the web was allowed to fall onto the fioor. When considerable static charge was present the fibre rolled up under the doffer comb of the card due to the attraction between it and the dofier. The fibre fell to the floor only when the weight of the roll was sufficient to overcome this electric attraction. In this way it was found that fibre dressed with a nonionic finish alone (Sample A) gave rise to noticeable static charge generation at a relative humidity (RI-I.) of 40% and a temperature of 75 F., whereas the fibre dressed with sodium nitrite together with the nonionic finish (Sample B) did not give noticeable static charge generation under these conditions, nor in fact at 35% RH. and 77 F., under which conditions Sample A gave rise to considerable static charge generation. The efiect of temperature was demonstrated by the fact that at 40% RH. and 80 F. neither Sample A nor Sample B showed noticeable static; at 40% RH. and 75 F., as noted above Sample A showed static but not Sample B; whereas at 40% RH. and 65 F. both samples gave noticeable static.

These results show clearly that the addition of sodium nitrite to the nonionic finish results in a considerable diminution of the tendency of the fibre to generate troublesome electrostatic charges during carding, and hence allows processing to continue without interruption at lower relative humidities or lower temperatures, or both, than would normally be the case.

Example 3 A few drops of a 20% aqueous solution of the nonionic finish containing the agent described in Example 2, were applied to ten samples of clean polished mild steel and allowed to dry. Five of the samples were then exposed to an atmosphere of 65% RH. and the other five to an atmosphere of 85% RH. at room temperature for 24 hours. (It may be noted that whereas at a given temperature static charge generation becomes Worse the lower the relative humidity, corrosion generally becomes worse the higher the relative humidity.) Further mild steel samples were treated in the same way with 20% solutions of the same nonionic finish containing the agent, plus 0.014 mole percent of (a) sodium nitrite, (b) sodium carbonate, (c) sodium bicarbonate, (d) sodium orthophosphate, and (e) sodium tetraborate, respectively.

Examination after a period of 24 hours showed that whereas slight corrosion had been caused by the nonionic finish alone at both 85% RH. and 65%, i.e. patches of rust had become visible, no corrosion was evident for any of the samples containing an inorganic salt at either of the relative humidities (except for slight traces at 85% RH. for one out of the five samples of nonionic finish with sodium carbonate).

It is inferred that the use of these salts as antistatic agents will not increase corrosion of metal parts of e.g. textile machinery, even when made of mild steel, but will tend to inhibit it. Thus if fibre dressed with nonionic polyethenoxy finish together with such salts is passed through a carding machine of which the clothing is made of mild steel, corrosion of the latter will not occur.

Example 4 The experiment described in Example 3 was repeated,

but using the nonionic finish described in Example 1, and the inorganic salts added were (f) sodium benzoate, (g) sodium chromate, (h) sodium silicate and (i) sodium nitrite, respectively. In this example, however, the solution concentration of each of the inorganic salts was 0.6% by weight.

Again, whereas slight corrosion was caused by the nonionic finish alone at both 85 RH. and no corrosion was evident for any of the samples containing the inorganic salt (f) (g) (h) or (i) at either of the relative humidities.

Example 5 Two samples of crimped polypropylene staple fibre of mean denier 5 (5.56 decitex) and mean length 4 inches, dressed with (A) 0.13% of the finish described in Example 2, and (B) 0.12% of the same finish together with 0.008% of sodium nitrite were processed on a carding machine at a relative humidity of 65% and a temperature of 68 F. It was found that fibre dressed with the nonionic finish alone gave rise to considerable static charge generation, whereas the fibre dressed with sodium nitrite together with the nonionic finish did not give noticeable static charge generation under these conditions.

What We claim is: Textile materials comprising fibers and filaments of a member of the group consisting of polyethylene terephthalate and polypropylene having an antistatic surface coating comprising (a) 0.050.3% on the weight of said fibers and filaments of a member of the class consisting of a condensate of lauric acid with ethylene oxide in a molar ratio of about 1:9, a condensate of cetyl and oleyl alcohols with ethylene oxide in a molar ratio of about 1:3.5, a condensate of cetyl amine with ethylene oxide in a molar ratio of about 1:12, a condensate of dodecyl mercaptan with ethylene oxide in a molar ratio of 1:6, and a condensate of stearic acid with approximately 9 moles of ethylene oxide and (b) 0.001 to 0.05% on the weight of said fibers and filaments of a salt selected from the group consisting of potassium carbonate, sodium bicarbonate, sodium phosphate, sodium chromate, sodium benzoate, sodium silicate, lithium carbonate, sodium nitrite, sodium tetraborate and sodium carbonate.

References Cited UNITED STATES PATENTS 2,436,978 3/1948 Standley et al. 117139.5 X 2,461,043 2/1949 Eisen 1l7139.5 X 2,628,176 2/1953 Simon et al. 117-138.8 2,664,409 12/ 1953 Aickin et al.

2,740,759 4/1956 Maeder et al 252-8.9 X 2,955,960 10/1960 Batty et a1 117-1388 3,009,830 11/1961 Levine 117-1395 WILLIAM D. MARTIN, Primary Examiner.

T. G. DAV-IS, Assistant Examiner. 

